Method of controlling the operation of applying a succession of discrete coupling elements

ABSTRACT

A method of controlling the operation of applying discrete coupling elements one at a time onto a stringer tape, which comprises counting the number N 1  of coupling elements entering a chute and comparing the number N 1  thus counted with the number R of reovlutions of a motor driving a means of applying the elements to the tape thereby incessantly monitoring the inventory Nc of the elements in the chute.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method of controlling the operation ofapplying a succession of discrete coupling elements one at a time onto astringer tape in the manufacture of slide fasteners.

2. Prior Art

Various methods and means have been devised for controlling theoperation of applying an array of discretely formed coupling elementsone at a time onto a stringer tape which is intermittently moved. Onesuch typical method relies on the use of a number of usually about threeto four photoelectric detectors provided along the length of a feedchute, wherein an uppermost detector is preset to determine a normaloperating speed; a plurality of intermediate detectors are set to reducethe operating speed stepwise or progressively; and a lowermost detectoris preset to discontinue the application of coupling elements to thestringer tape. This prior art method has a drawback in that when theoperating speed of applying coupling elements to the tape is changedfrom high to low or vice versa, the apparatus including means of movingthe stringer tape and means of applying the coupling elements to thetape would lag behind due to inertia in responding to such speedvariations, resulting in irregularities in the inter-spacing betweenadjacent coupling elements mounted on the tape. Another drawback is thatthe inventory or amount of coupling elements present in the feed chuteis made known only at the areas at which the detectors are installed,but not elsewhere in the chute so that there would inevitably developcertain time loss in the production of slide fasteners as a whole.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a method ofcontrolling the operation of applying a succession of discrete couplingelements at substantially constant or equal intervals along alongitudinal edge of a stringer tape by continuously or incessantlymonitoring the inventory of coupling elements within a feed chutethrough which the elements are fed and transferred onto the tape.

This and other objects and features of the invention will appearapparent from the following description taken in conjunction with theaccompanying drawings.

According to the invention, there is provided a method of controllingthe operation of applying a succession of discrete coupling elements,supplied through a chute, onto a stringer tape at constant intervalsalong a longitudinal edge thereof, which method comprises the steps ofdetecting and counting the number N₁ of the coupling elements which haveentered the chute at one end thereof; subtracting from the number N₁ thenumber N₂ of the coupling elements which have been applied onto the tapethereby monitoring the inventory or number Nc of the coupling elementswithin the chute; and adjusting the speed of applying the couplingelements to an extent corresponding to the number Nc of the couplingelements being monitored.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram utilized to illustrate a control devicefor carrying the inventive method into practice;

FIG. 2 is a graph showing the rate of speed of a motor plotted againstthe number of coupling elements present in a feed chute;

FIG. 3 is a fragmentary plan view of a slide fastener;

FIG. 4 is a perspective view of an apparatus for feeding and applying asuccession of coupling elements one at a time onto a stringer tape;

FIG. 5a is a diagrammatic elevational view of the coupling element shownmounted astride the tape edge; and

FIG. 5b is a diagrammatic elevational view of the coupling element shownclamped onto the tape edge.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings and firstly to FIG. 4, there is shown anapparatus 10 for feeding and applying discrete coupling elementssuccessively one at a time to a longitudinal beaded edge Ta of astringer tape T. Each coupling element E has a coupling head Ea and apair of bifurcated legs Eb which are mounted astride of and clamped tothe tape edge Ta in a manner to be hereinafter described. The apparatus10 comprises an element feed unit 11 for supplying the coupling elementsE and an element applying unit 12 for applying the coupling elements tothe tape T. The feed unit 11 comprises a vertically disposed chute 13having an elongate guide slot 14 through which the coupling elements Eare allowed to move downwardly by gravity, and a horizontally disposedslide 15 supported on a base 16 for horizontal reciprocating movementeffected by suitable drive means not shown.

A pocket 17 is formed in the slide 15 for receiving a leading orlowermost one E₁ of the coupling elements E from the chute 13. Atransfer opening 18 is formed extending through the slide 15 and thebase 16 and registrable with the pocket 17 for receiving the couplingelement E which has been transferred on the slide 15. The element E islet fall by gravity through the transfer opening 18 onto the tape Twhich is oriented with its beaded edge Ta held upright and in parallelopposed relation to the base 16 and in registry with the transferopening 18. As the element E is mounted with its bifurcated legs Ebastride the tape edge Ta as

shown in FIG. 5ait is held so in place by a vertical positioning member19 vertically movable to hold the upper surface of the head Ea of theelement E and a pair of horizontal positioning members 20 horizontallymovable toward and away from each other and adapted to hold the elementhead Ea from both sides thereof as shown in FIG. 5b. With the element Ethus held in position, it is firmly attached to the tape T by means of apair of punches 21 which clamp or clinch the respective legs Eb of theelement against the tape edge Ta in a manner illustrated in FIG. 5b. Thepunches 21 are driven by an electric motor M (FIG. 1) which iscontrolled in a manner later described so that one each revolutionthereof per unit time provides one cycle of reciprocation of the punches21 to complete the attachment of one coupling element E to the tape T.

Referring now to FIG. 1, there is schematically illustrated a controldevice generally designated at 100 which is provided according to apreferred embodiment for carrying into practice the inventive method ofcontrolling the operation of the element feeding and applying apparatus10 so as to ensure attachment of the coupling elements E properly atequal intervals or at a constant element-to-element pitch on and alongthe longitudinal edge Ta of the stringer tape T. The control device 100essentially comprises an upper-limit photoelectric sensor 110 located atthe upper end of the feed chute 13 for detecting the number N₁ ofcoupling elements E entering the chute 13 and a lower-limitphotoelectric sensor 120 located at the lower end of the chute 13 fordetecting the number N₂ of coupling elements E entering the elementapplying unit 12.

A main control circuit means 130 receives a signal for example in theform of a pulse from each of the sensors 110 and 120 and includes acounter for counting the number N₁ of pulses transmitted from theupper-limit sensor 110 and a memory for storing the number of suchpulses counted. The circuit means 130 further includes a controllerprogrammed to maintain the number R of revolutions of the motor Msubstantially in proportion to the number Nc of coupling elements Ewithin the chute 13.

A detector 140 detects the number R of revolutions of the motor Mcorresponding to the number Nc of elements E in the chute 13 andtransmits a corresponding signal to the controller in the main controlcircuit means 130 which in turn transmits a control signal representingthe number N₁ of elements E detected, i.e. the number R of revolutionsmade by the motor M, to a frequency inverter 150. This inverter controlsthe motor M by varying the frequency of a power therefor in accordancewith the number Nc of elements E increased or decreased within the chute13.

The arrangement of the control device 100 is such that the number Nc ofcoupling elements E or the inventory thereof within the chute 13 at anygiven point of time can be monitored by counting and comparing thenumber N₁ of elements E passing through the upper-limit sensor 110 withthe number R of revolutions of the motor M. Ideally, the inventory Nc ofcoupling elements E in the chute 13 is constant between the upper-limitsensor 110 and the lower-limit sensor 120 so that the motor M remains ata constant preset rate of speed. If however for some reason theinventory Nc of elements E in the chute 13 is reduced, this is readilydetected by the detector 140 to reduce the speed of the motor Maccordingly. Such instance would often occur when the supply of couplingelements E to the chute 13 is discontinued due to operational failure ofa vibratory bowl 160 on a parts feeder 170 or due to the absence ofelements E in the bowl 160, leading to discontinued function of theupper-limit sensor 110.

FIG. 2 graphically plots the number R of revolutions or speed of themotor M against the number Nc of coupling elements E within the chute13, from which it is evident that both numbers R and Nc remain in directproportion provided a substantial level of inventory of elements E isestablished in the chute 13. However, if the inventory or number N ofelements is reduced for one reason or another drastically to a level Nn,the motor M is preset to continue operation at a predetermined minimumrate of speed required to maintain the punches 21 in proper clampingoperation, and as the inventory Nc of elements E becomes finally nil inthe chute 13 as indicated at Ns in FIG. 2, this is detected by thelower-limit sensor 120 to transmit a corresponding signal to the maincontrol circuit means 130 so as to discontinue the operation of themotor M. When the supply of coupling elements E from the parts feeder170 is resumed, the number N of elements E gradually increases in thechute 13 with corresponding increase in the speed or number R ofrevolutions per unit time of the motor M until the inventory Nc ofelements E is built up in the chute 13 such that the speed R of themotor M becomes proportionate to the number N of elements E.

FIG. 3 shows a slide fastener F carrying rows of discrete couplingelements E on respective longitudinal edges Ta of a pair of stringertapes Ta, the coupling elements E being aligned in properly or equallypitched relation maintained by the practice of the invention such thatthey can be coupled and uncoupled smoothly by a slider S in a mannerwell known in the art.

Advantageously, the method of the invention provides incessantmonitoring of the inventory of coupling elements in the chute 13 toenable a continuous or uninterrupted operation of applying the elementsE one at a time at controlled rate of speed onto the stringer tape Tregardless of changes in the number Nc of elements E in the chute 13 andthus to ensure the attachment of elements E at constant, equal intervalsalong the tape edge Ta.

Obviously, various modifications and variations of the present inventionare possible in the light of the above teaching. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A method of controlling the operation of applyinga succession of discrete coupling elements, supplied through a chute,onto a stringer tape at constant intervals along a longitudinal edgethereof, which method comprises the steps of:(a) detecting and countingthe number N₁ of said coupling elements which have entered said chute atone end thereof; (b) subtracting from said number N₁ the number N₂ ofsaid coupling elements which have been applied onto said tape therebymonitoring the inventory or number Nc of said coupling elements withinsaid chute; and (c) adjusting the speed of applying said couplingelements to an extent corresponding to said number Nc of said couplingelements being monitored.
 2. A method according to claim 1 furthercomprising maintaining the rate of speed of applying said couplingelements in direct proportion with the inventory Nc of said couplingelements in said chute.